Combustion chemical vapor deposition (combustion CVD) is a relatively new technique for the growth of coatings. Combustion CVD is described, for example, in U.S. Pat. Nos. 5,652,021; 5,858,465; and 6,013,318, each of which is hereby incorporated herein by reference in its entirety.
Conventionally, in combustion CVD, precursors are dissolved in a flammable solvent and the solution is delivered to the burner where it is ignited to give a flame. A substrate is then passed under the flame to deposit a coating.
There are several advantages of combustion CVD over traditional pyrolytic deposition techniques (such as CVD, spray and sol-gel, etc.). One advantage is that the energy required for the deposition is provided by the flame. Thus, combustion CVD is amenable to comparatively low substrate temperatures and non-traditional substrates (e.g., plastics, etc.). Another advantage is that combustion CVD techniques do not necessarily require volatile precursors. If a solution of the precursor can be atomized/nebulized sufficiently, the atomized solution will behave essentially as a gas and can be transferred to the flame without requiring an appreciable vapor pressure from the precursor of interest. Also, since the flame temperature is quite high, thermally unstable precursors are not necessarily required.
In combustion CVD, if the flame is self-supporting (e.g., as with a propane-air mixture), the solvent need not be flammable. Thus, the inventor of the instant application has recognized that using water as a solvent would be advantageous for combustion CVD, as a water solvent would be easy to handle, environmentally friendly, and very inexpensive, especially when compared to organic solvents.
However, it is believed that only one study to-date has described the viable use of aqueous precursor solutions in connection with combustion CVD (see Davis, M. J. et al., “Growth of Thin Films of Molybdenum and Tungsten Oxides by Combustion CVD Using Aqueous Precursor Solutions.” Chemical Vapor Deposition, vol. 10, no. 1 (2004), p. 29). In this study, molybdenum and tungsten oxides were deposited from the involatile inorganic salts ammonium molybdate and ammonium metatungstate, respectively, in aqueous solution. Coatings from about 20 nm up to 100 nm were grown, depending on the deposition conditions.
Based on this study, the inventor of the instant application has recognized the feasibility of depositing coatings of TiO2 from aqueous precursor solutions. TiO2 or other titanium oxide coatings provided by combustion deposition open up opportunities for low cost production of multilayer AR (MLAR) designs and low maintenance glass applications, comparable to more conventional photocatalytic and super-hydrophilic coatings. Depositing coatings of TiO2 (or other titanium oxide forms) from aqueous precursor solutions, for example, advantageously would be easy to handle, environmentally friendly, and very inexpensive.
Thus, it will be appreciated that it would be advantageous to identify and provide an aqueous based precursor system for the deposition of coatings (e.g., TiO2 coatings) via combustion deposition.
In certain example embodiments of this invention, a method of applying a coating to a glass substrate using combustion deposition is provided. A glass substrate having at least one surface to be coated is provided. A reagent and a carrier medium are selected, and the reagent and the carrier medium are mixed together to form a reagent mixture. The reagent is selected such that at least a portion of the reagent forms the coating. An aqueous based precursor to be combusted with the reagent mixture is introduced. Using at least one flame, at least a portion of the reagent mixture and the aqueous based precursor are combusted to form a combusted material. The combusted material comprises non-vaporized material. The glass substrate is provided in an area so that the glass substrate is heated sufficiently to allow the combusted material to form the coating, directly or indirectly, on the glass substrate.
In certain example embodiments of this invention, a method of applying a coating to a substrate using combustion deposition is provided. A substrate having at least one surface to be coated is provided. A reagent and a carrier medium are selected, and the reagent and the carrier medium are mixed together to form a reagent mixture. The reagent is selected such that at least a portion of the reagent forms the coating. An aqueous based precursor to be combusted with the reagent mixture is introduced. The aqueous based precursor is an organic salt of titanium. Using at least one flame, at least a portion of the reagent mixture and the aqueous based precursor are combusted to form a combusted material. The substrate is provided in an area so that the substrate is heated sufficiently to allow the combusted material to form the coating, directly or indirectly, on the substrate. The deposited coating is TiO2.
In certain example embodiments of this invention, a method of applying multiple coatings to a substrate using combustion deposition is provided. A glass substrate having at least one surface to be coated is provided. There is formed a first reagent mixture including a first reagent selected so that at least a portion of the first reagent forms a first coating. There is formed a second reagent mixture including a second reagent selected so that at least a portion of the second reagent forms a second coating. At least one aqueous based precursor to be combusted is introduced. Using at least one flame, at least a portion of the first reagent mixture is combusted to form a first combusted material. The first combusted material comprises non-vaporized material. Using at least one flame, at least a portion of the second reagent mixture is combusted to form a second combusted material. The second combusted material comprises non-vaporized material. The substrate is provided in an area so that the substrate is heated sufficiently to allow the first combusted material and the second combusted material to form a first coating and a second coating, respectively, directly or indirectly, on the substrate.